The present invention relates to a method for controlling a work function of a vehicle that has a forward gear position for driving the vehicle forwards and a reverse gear position for driving the vehicle backwards, comprising detection of an operating parameter and, in response to this, production of a parameter signal for a control unit, and control of the work function that is carried out by the control unit on the basis of the value of the parameter signals.
The invention also relates to a device for carrying out the method according to the invention and a work vehicle comprising the control device.
The work function can, for example, be the control response, that is to say the turning of the wheels in the case of turning of the steering wheel, or the hydraulic working pressure of a machine that works by hydraulics. The invention is, however, particularly suitable for controlling the selection of the gear mode of a work vehicle, such as a wheel loader, with automatic transmission with several gear modes. For the purpose of exemplification, it will be described with reference to such an application. The invention can, of course, also be applied to other types of work vehicle, such as a backhoe or a so-called skid steer vehicle.
Modern wheel loaders with automatic gearboxes currently use various so-called gear modes or gear functions according to a particular gear-change strategy. The gear modes differ in that changing to a higher gear, changing up, is carried out at different minimum engine speeds for the different gear modes, for changing between corresponding gears, and changing to a lower gear is carried out at different minimum vehicle speeds. In conventional wheel loaders, these modes are selected manually by an operator using a control, a so-called APS-control. Through EP 0 715102, a method is already known for controlling gear modes in an automatic vehicle transmission on the basis of parameter signals that represent operating conditions for the vehicle, the driver's driving intention, and the road conditions. In particular, the operating parameters represent the gradient of a road on which the vehicle is being driven. It is, however, normal for a vehicle of the wheel loader type, on which automatic transmissions of the type mentioned are usually found, to work on an essentially level surface. Even in such cases, there is a desire, depending upon the operation of the vehicle, to be able to select a gear mode that is the most expedient with regard to efficiency, fuel consumption, environmental factors, etc.
It is desirable to provide a method of the type mentioned in the introduction that provides important information for controlling a work function, preferably selection of gear mode, and that carries out controlling of the work function, or selection of gear mode, on the basis of the information.
According to an aspect of the present invention, a method for controlling a work function of a vehicle that has a forward gear position for driving the vehicle forwards and a reverse gear position for driving the vehicle backwards, comprises detection of an operating parameter and, in response to this, production of a parameter signal for a control unit, and control of the work function that is carried out by the control unit on the basis of the value of the parameter signals. The parameter signal represents the total distance that the vehicle is driven in an individual sequence with at least one of the forward gear position and the reverse gear position. In other words, the distance driven between two changes of direction of the vehicle is recorded, and the automatic control of the work function is based on the outcome of the recording. An individual recording of a distance driven is commenced at the moment there is a change of gear from forward gear position to reverse gear position or vice versa. The recording of the distance is terminated when the next change of gear back to the forward gear position or the reverse gear position is carried out. These changes between forward gear position and reverse gear position are assumed to be carried out manually by the driver of the vehicle. It is quite possible only to record the distance driven forwards or only to record the distance driven backwards, but it is preferable for the distance to be recorded in both directions. By measuring distances driven in this way and basing the control of any work function, for example the selection of gear mode, on these, it is possible to adapt the control of the work function in question to the load cycle according to which the vehicle is currently assumed to be working.
According to an aspect of the invention, the vehicle has an automatic transmission that is arranged to change gear according to a plurality of gear modes, with the gear mode being selected on the basis of the parameter signal. The gear modes differ in that changing to a higher gear is carried out at different minimum engine speeds.
According to an aspect of the invention, the method comprises generation of a parameter signal from each of a plurality of consecutive sequences and comparison of the parameter signals and control of the work function or selection of gear mode on the basis of the parameter signal that represents the longest distance driven. For each gear mode, there is a thus a range of distances for which precisely that gear mode is selected. Which gear mode is selected or how a particular work function is controlled thus depends upon the range in which the longest measured distance is to be found.
Suitably, only a certain maximal number of parameter signals or recordings of previous distances driven are recorded for comparison in the control unit.
At the commencement of the vehicle being driven, the control unit preferably selects automatically a highest gear mode, that changes to a higher gear at a lower minimum engine speed than other gear modes. As soon as a first parameter signal has been obtained, a review of the selection of gear mode is carried out. This principle is, moreover, generally applicable for controlling other work functions than the selection of gear mode.
In a device according to an aspect of the invention, the operating parameter represents the distance the vehicle has been driven in an individual sequence with at least one of the forward gear position and the reverse gear position.
A vehicle according to an aspect of the invention has an automatic transmission that is arranged to change gear according to a plurality of gear modes, with the control unit being arranged to select the gear mode on the basis of the parameter signal.
The gear modes differ in that corresponding changes to a higher gear take place at different minimum engine speeds.
In order to make possible an automatic implementation of a preferred embodiment of the method according to the invention, the control unit is advantageously arranged to collect from the sensor a parameter signal from each of a plurality of consecutive sequences and the control unit is arranged to compare the parameter signals and to control the work function or select the gear mode on the basis of the parameter signal that represents the longest distance driven.
In addition, the control unit is preferably arranged, when driving of the vehicle commences, to select the highest gear mode that changes to a higher gear at the lowest minimum engine speed of all the gear modes.
In addition, the sensor should be arranged, during an ongoing sequence with the transmission in the forward gear position or reverse gear position, to send a signal continually to the control unit concerning the distance traveled, and the control unit should be arranged, when the parameter signal represents a distance that exceeds the greatest distance that is represented by the parameter signals for the immediately preceding sequences, to change to the next higher gear mode. This means that change of gear mode can take place even before a finally-complete distance in a gear position has been measured. It can suffice, during an ongoing measurement, for the distance to exceed the longest distance measured so far or a predetermined value, in order for an immediate change to a higher gear mode to be required by the control unit.
Additional characteristics and advantages of the present invention will be apparent from the following description.